PROJECT SUMMARY Glioblastoma is highly resistant to chemo- and radiotherapy. Despite treatment, median survival is only 12-15 months. Tumor cells rely upon elevated stress response pathways to survive and maintain a rapid proliferative rate in the harsh tumor microenvironment. Glioblastoma stem cells (GSCs) are particularly enriched in their ability to survive in the context of nutrient deprivation, high reactive oxygen species, DNA damage and radiation. Upregulation of heat shock proteins (HSPs) and the unfolded proteins response (UPR) promote cell survival during stress. These pathways are elevated in glioblastoma and knockdown induces chemosensitivity and cell death. The UPR specifically relieves ER stress, a key pathway of radiation-induced cell death. I have identified RSAD1 as a potential regulator of the UPR and thus a novel dependency in GSCs. There are currently no published studies characterizing the function of RSAD1. RSAD1 is upregulated in glioblastoma and is correlated with worse survival, and my preliminary evidence demonstrates that RSAD1 knockdown significantly impairs proliferation in GSCs. I found that RSAD1 binding partners enrich for UPR regulators and HSPs. The goal of this research is to test the hypothesis that RSAD1 promotes survival in GSCs through activation of the UPR. Given the important role of the UPR in inducing stress resilience, inhibition of RSAD may act as a chemo- or radiosensitizer of GSCs, in addition to independently impairing proliferation. RSAD1 may therefore be a novel target for synergistic therapy in glioblastoma.